Only valid for active forum users. Active means at least 30 postings within the last 30 days (no spam postings). This will automatically being checked at www.starbike.com shopping basket so make sure that you are logged in at the WW board!If there does not appear a WW discount position when you check out you do not have enough postings!

Check this. You won't be able to fit it in an Aeroad, but for those who are experiencing it in other bikes. Cane Creek has the Viscoset, a headset with dampening technology to address issues like this.

BTW: Now I recall that the aeroad has a setting in the fork to modify the trail. I don't know which one is the default position. Maybe you can switch it to the more relaxed position since I read somewhere that increasing the trail reduces chances of resonance.

Aeroad disc is thru-axle, so only one position. I've not been able to find out on the interwebs whether this fix position corresponds to the "stable" or the "agile" setting on the rim brake Aeroad, or if it sits somewhere between the two.

New member here, I felt compelled to register after reading this thread as I have a very similar experience. I bought an Aeroad CF SLX 9 Disc size M- albeit on DT Swiss wheels at 48mm depth. Initial impressions great, a fast aggressive bike, enough comfort for the odd 100 miler and perfectly suited to the rolling terrain I cover on most rides. Subjectively it feels "fast" and stops just as well. On the first few rides, there was a feeling of twitchiness on the front end, but I dismissed this as a learning curve for me on the new bike. The first fast long descent had me learning all about speed shimmy the hard way. It kicked in at 43MPH on a straight road. Violent lateral shaking, terrifying and persistent until I brought the bike to a complete halt. I add this is not related to the brakes at all, the shimmy started before any braking was applied. Checked the bike et voila, loose headset and a slow puncture on the rear, surely one or both variables were to blame? Regardless, I gave it a full mechanical once over, the (new) wheels seemed well balanced, new Conti GP4000s were well seated, no cracks anywhere on the frame etc.

So off we go again, slowly building confidence in the bike and trying to focus on riding technique on descents - weight distributed well behind the BB, unloading weight from the saddle towards the pedals to lower centre of gravity, relaxed grip on the bars, one knee on the top tube. A few epic sportive rides with no issues, fast winding descents, some gusty sidewinds, but nothing unusual in the handling department.. Then when I least expected it, cresting a local hill with a descent at about 10%, a very slight sidewind and whoa, an almost comical low frequency shimmy at 28MPH. This was easily killed by clamping the top tube with both knees and a dab of brakes, but very disappointing.

This got me thinking more about weight distribution - I'm no young racer and maybe a lack of core strength means too much weight on the bars when down in the drops (I use all the spacers except the final 2mm one). So from then on I decided to descend on the hoods if only to prove the point. However, same local hill, the slightest sidewind and sure enough, the same ridiculous low frequency shimmy, which came on even whilst I was still pedalling. Easily killed, but not before it had pitched me over to the wrong side of the road.

So given all of this, what recourse is there? I don't think the frame is defective or subject to any warranty claim with Canyon. However it seems odd to have such serious stability problems on such a well received bike, used in the pro peleton and apparently well regarded by so many. My last bike was a Tarmac, almost as aggressive a fit and no issues at all. Any suggestions or should we be changing frames before we get into serious accidents? Any others with similar issues?

The handlebars are indeed very loose (they move side-to-side super easily), but do not knock in any direction. As long as it's not knocking, does the steering need to be any tighter? (My understanding has always been: as loose as you can as long as it doesn't knock...)

You should elaborate on this, nothing should be 'loose' on your bike. You mean the headset doesn't bind when you turn the front wheel side to side?

I had issues tightening the Acros headset when I first put the bike together. I don't have a 1.5Nm torque wrench, so I don't think I was tightening the adjustment clamp enough. I honestly don't like the way the Acros is secured, I'd rather use the top cap for preload with an expander plug like a normal headset.

Are you following the proper Acros tightening technique? I honestly think that is what is causing the issue. Plus, the steering in this bike is just twitchy, way more than my previous SL4 tarmac.

I really don't believe in the resonant frequency thing. No way a manufacturer wouldn't design around that problem, regardless of rider weight.

New member here, I felt compelled to register after reading this thread as I have a very similar experience. I bought an Aeroad CF SLX 9 Disc size M- albeit on DT Swiss wheels at 48mm depth. Initial impressions great, a fast aggressive bike, enough comfort for the odd 100 miler and perfectly suited to the rolling terrain I cover on most rides. Subjectively it feels "fast" and stops just as well. On the first few rides, there was a feeling of twitchiness on the front end, but I dismissed this as a learning curve for me on the new bike. The first fast long descent had me learning all about speed shimmy the hard way. It kicked in at 43MPH on a straight road. Violent lateral shaking, terrifying and persistent until I brought the bike to a complete halt. I add this is not related to the brakes at all, the shimmy started before any braking was applied. Checked the bike et voila, loose headset and a slow puncture on the rear, surely one or both variables were to blame? Regardless, I gave it a full mechanical once over, the (new) wheels seemed well balanced, new Conti GP4000s were well seated, no cracks anywhere on the frame etc.

So off we go again, slowly building confidence in the bike and trying to focus on riding technique on descents - weight distributed well behind the BB, unloading weight from the saddle towards the pedals to lower centre of gravity, relaxed grip on the bars, one knee on the top tube. A few epic sportive rides with no issues, fast winding descents, some gusty sidewinds, but nothing unusual in the handling department.. Then when I least expected it, cresting a local hill with a descent at about 10%, a very slight sidewind and whoa, an almost comical low frequency shimmy at 28MPH. This was easily killed by clamping the top tube with both knees and a dab of brakes, but very disappointing.

This got me thinking more about weight distribution - I'm no young racer and maybe a lack of core strength means too much weight on the bars when down in the drops (I use all the spacers except the final 2mm one). So from then on I decided to descend on the hoods if only to prove the point. However, same local hill, the slightest sidewind and sure enough, the same ridiculous low frequency shimmy, which came on even whilst I was still pedalling. Easily killed, but not before it had pitched me over to the wrong side of the road.

So given all of this, what recourse is there? I don't think the frame is defective or subject to any warranty claim with Canyon. However it seems odd to have such serious stability problems on such a well received bike, used in the pro peleton and apparently well regarded by so many. My last bike was a Tarmac, almost as aggressive a fit and no issues at all. Any suggestions or should we be changing frames before we get into serious accidents? Any others with similar issues?

I also felt twitchy when I test ride a Aeroad. But everybody else spoke highly after they tried Aeroad. Weird.

Freddiekaberman: thanks for posting your experience. Sorry to hear about your issues. Glad you are OK.

About the "loose handlebars", I meant they turn side-to-side easily with zero resistance. The headset is tight, no knocking at all with front brake on, trying to rock bike back and forth on the front wheel.

I could not tighten the headset using the Accros special procedure of yore, since it all ears they've changed the design and it now tightens via the top cap bolt like regular headsets.

As regards my bike's stability, I've done a race where I descended about 1800 meters as fast as gravity would take me, consistently in the mid 60 km/h, and as much as 71 km/h with no problem, but on different wheels now (Enve 4.5 AR) instead of the Strikes, and always being mindful to be in the drops, weight the pedals when turning and always pressing the top tube with at least one knee. So far so good...

Check this. You won't be able to fit it in an Aeroad, but for those who are experiencing it in other bikes. Cane Creek has the Viscoset, a headset with dampening technology to address issues like this.

BTW: Now I recall that the aeroad has a setting in the fork to modify the trail. I don't know which one is the default position. Maybe you can switch it to the more relaxed position since I read somewhere that increasing the trail reduces chances of resonance.

Aeroad disc is thru-axle, so only one position. I've not been able to find out on the interwebs whether this fix position corresponds to the "stable" or the "agile" setting on the rim brake Aeroad, or if it sits somewhere between the two.

I really don't believe in the resonant frequency thing. No way a manufacturer wouldn't design around that problem, regardless of rider weight.

Physics doesn't care if you believe in it or not. Every system has a resonant frequency (many in some cases) the problem with a bike is the "designed" bit is only ~10% of the mass. Or it could be 5% of the mass. And rider morphology is not fixed.

You get it in motorbikes, aeroplanes, bridges, cars. But all these are easier to design out as the mass distribution and structure are far easier to control. (except motorbikes.)

I really don't believe in the resonant frequency thing. No way a manufacturer wouldn't design around that problem, regardless of rider weight.

Physics doesn't care if you believe in it or not. Every system has a resonant frequency (many in some cases) the problem with a bike is the "designed" bit is only ~10% of the mass. Or it could be 5% of the mass. And rider morphology is not fixed.

You get it in motorbikes, aeroplanes, bridges, cars. But all these are easier to design out as the mass distribution and structure are far easier to control. (except motorbikes.)

This would mean that every bike would behave like this at some point and they don't. I've never experienced it on any bike and I descend regularly at fast speeds.

This would mean that every bike would behave like this at some point...

Correct.

...and they don't. I've never experienced it on any bike and I descend regularly at fast speeds.

It just takes the right circumstances.

Shimmy is more likely

- with a flexible system (the natural frequency drops as flex increases, bringing more typical speeds into the range where wheel rotation might match the system's natural frequency).
- with larger frames (larger frames are commonly more flexible)
- heavier bike+rider system (natural frequency decreases as weight increases)

Many riders don't ever experience it. But shimmy is still resonance at natural frequency (or a multiple of it).

If you can change the stiffness or mass of the system you can change its natural frequency. Goal: stiffer & lighter, to raise the natural frequency to speeds you "never" ride at. Usually a frame change is needed. (Maybe Canyon would send Freddie an Ultimate?)

Failing that, learn to control the shimmy: either clamp the top tube or raise your butt off the saddle.

I could not tighten the headset using the Accros special procedure of yore, since it all ears they've changed the design and it now tightens via the top cap bolt like regular headsets.

Confused. I have the newest Aeroad disc and mine uses the standard Acros headset. I didn't know what it was and tried tightening the top cap for preload and immediately stripped it. I'm eventually going to add a normal expander plug with a stronger top cap bolt for preload, but I couldn't get the original plug out yet.

dcorn - mine also has a regular headset with expander bolt, but with the strange bolt on the headset top cap (the part that fits on top of the head tube, underneath the spacers). I also damaged mine by over-tightening, Canyon sent me a replacement for free. In my case, I completely stripped down and re-torqued the headset to my complete satisfaction, but it didnt make an ounce of difference to the stability and tendency to shimmy under the right conditions. I think Damon has it right, no manufacturer intends this to happen, but they can't cater for every single rider under all conditions.

I could not tighten the headset using the Accros special procedure of yore, since it all ears they've changed the design and it now tightens via the top cap bolt like regular headsets.

Confused. I have the newest Aeroad disc and mine uses the standard Acros headset. I didn't know what it was and tried tightening the top cap for preload and immediately stripped it. I'm eventually going to add a normal expander plug with a stronger top cap bolt for preload, but I couldn't get the original plug out yet.

Do you not have a disc bike? Or not Di2 with the H11 handlebar?

I have an Aeroad CF SLX Disc 8.0 Di2 with the H11. Set up the same as Freddie's (i.e., bolt on headset cap seems to do nothing, and steering tightened through top cap bolt, which is easy to strip indeed.

This would mean that every bike would behave like this at some point...

Correct.

...and they don't. I've never experienced it on any bike and I descend regularly at fast speeds.

It just takes the right circumstances.

Shimmy is more likely

- with a flexible system (the natural frequency drops as flex increases, bringing more typical speeds into the range where wheel rotation might match the system's natural frequency).
- with larger frames (larger frames are commonly more flexible)
- heavier bike+rider system (natural frequency decreases as weight increases)

Many riders don't ever experience it. But shimmy is still resonance at natural frequency (or a multiple of it).

If you can change the stiffness or mass of the system you can change its natural frequency. Goal: stiffer & lighter, to raise the natural frequency to speeds you "never" ride at. Usually a frame change is needed. (Maybe Canyon would send Freddie an Ultimate?)

Failing that, learn to control the shimmy: either clamp the top tube or raise your butt off the saddle.

Then the bike is fine again.

Also wanted to take a moment to thank Damon for his contribution to this thread. It's a privilege to be able to benefit from the considerable knowledge and experience of someone who has been at the forefront of carbon bike design for the last few decades! Thank you for taking the time to educate us!

Also wanted to take a moment to thank Damon for his contribution to this thread. It's a privilege to be able to benefit from the considerable knowledge and experience of someone who has been at the forefront of carbon bike design for the last few decades! Thank you for taking the time to educate us!

Thanks Bordcla. Usually I don't have much time, but I like to participate when I can.